QuoteReplyTopic: The Looming Threat of Yellow Fever Posted: May 31 2017 at 10:44am

Three years ago, the West African Ebola epidemic set off a worldwide panic and the biggest global-health security crisis in years. Then Zika struck and the reality of those transmittable disease threats was brought even closer to home in the United States, with more than 5,000 cases reported and America still on high alert. Yet today, an even greater potential threat to the world is sweeping across Brazil.

The disease, yellow fever, is a deadly virus that spreads as rapidly as Zika, with symptoms that can be as horrific as Ebola. It is transmitted by certain species of mosquito, including the same Aedes aegypti that carries Zika. Up to 15 percent of those bitten become severely ill, with symptoms that include black vomit and bleeding from the nose, mouth and eyes. For up to half of those who develop severe symptoms, yellow fever ends in a painful death.

Until about a century ago, the disease regularly caused urban epidemics in the United States, including one in Philadelphia that killed 10 percent of the population in 1793, forcing President George Washington and others in his administration to flee what was then the nation’s capital.

Now, with Brazil facing an unusually large outbreak of yellow fever — there are 715 confirmed cases, more than 820 suspected cases and 240 confirmed deaths — another global health crisis looms. So far, the outbreaks have largely been confined to sparsely populated jungle areas. There is serious concern, however, that if the virus starts spreading in a major city, health authorities will be ill equipped to contain it. Rio de Janeiro, for one, is aggressively vaccinating its citizens in hopes of inoculating 12 million by the end of the year.

Yellow fever already kills upward of 30,000 people a year worldwide, though in 2013 as many as 60,000 might have died from the disease. With the threat of yellow fever returning to regions where it was once expunged, that number could rise significantly. What is particularly worrying is the possibility of yellow fever taking hold in previously unaffected parts of the world like Asia. The combination of Aedes aegypti being prevalent there and about 1.8 billion unvaccinated people living in densely populated parts of that continent makes for a potential disaster.

While there is no cure for yellow fever, a licensed vaccine has long been available that is safe, affordable and highly effective, providing lifetime protection with just one dose.

Last year, Angola’s capital, Luanda, endured the world’s largest outbreak of yellow fever in three decades. A surge in demand resulted in vaccine shortages, particularly when the disease spread to the neighboring Democratic Republic of Congo and farther afield to Kenya. With a large Chinese work force in Angola, many whom were unvaccinated, 11 cases reached China. Miraculously those were contained without further spread.The shortages made the situation so desperate that the World Health Organization and Unicef had to resort to fractional dosing in Kinshasa, capital of the Democratic Republic of Congo, administrating one-fifth of a normal dose. We got lucky: The Brazilian manufacturer made available up to 2.5 million doses of the vaccine, and the outbreak was curbed.

Now, the situation has reversed. Having already distributed 15 million vaccine doses since the outbreak began in December, Brazil has been forced to request 3.5 million doses from the International Coordinating Group on Vaccine Provision, which oversees emergency stocks financed by Gavi, the Vaccine Alliance, the nonprofit group I manage. With a global emergency stockpile of six million doses and about 12 million people living in and around Rio, it is easy to see why public health experts are worried. If Rio and one other major city experience an outbreak, it is doubtful whether stocks could be replenished fast enough to keep up with demand.

The proportion of people living in urban areas, where diseases can spread far more rapidly than in rural areas with scattered populations, is forecast to rise from one-third of the planet’s population in 1950 to two-thirds by 2050. Clearly, we need to revise our risk assessments for infectious diseases to reflect this trend. But just how large should vaccine stockpiles be? And for how many cities should we prepare?

And while these emergency stockpiles are essential, if we have to call upon them we have in some way already failed. They should be our last line of defense. Instead, if we want to avoid a return of the kind of urban epidemic that killed 5,000 people in Philadelphia two centuries ago, we need to prevent outbreaks from occurring in the first place. That means improving mosquito control and simultaneously increasing immunity against yellow fever through routine immunization and pre-emptive vaccination campaigns.

With winter arriving next month in South America, the outbreak will most likely be brought to heel. But as mosquito season approaches in the north, control measures will be essential if we want to avoid yellow fever following Zika’s path, making its way north through Latin America to southern states in the United States like Florida.

And if, or when, it arrives, awareness will also be critical to prevent its spread, especially because very few doctors in the United States have ever seen a case and hardly anyone is vaccinated. As things stand, shortages are already affecting the availability of yellow fever travel vaccines in the United States.

History has shown that preventive approaches can be highly effective at controlling yellow fever, but if they are to work we first need to recognize there is a problem. To quote a long-ago Philadelphian, Benjamin Franklin, “an ounce of prevention is worth a pound of cure.”

You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot delete your posts in this forumYou cannot edit your posts in this forumYou cannot create polls in this forumYou cannot vote in polls in this forum